I just rebuilt my 123 ATE and took her out yesterday. Every thing works fine. Not hard to do. I did one side @ a time in case I needed to see a intact one. Read all you can on how to do this as there are some helpfull tips. Take you time and you too can rebuild your Calipers. Good luck.
Regards
2dieseljohn

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2dieseljohn
1979 300sd (283,000+) Road Trips
1983 240D 4-speed (350,000+) Daily Driver
1967 E-TypeS1 in bits and pieces